ANOMALOUS ANISOTROPY OF THE ELASTIC-CONSTANTS IN THE INDUCED SMECTIC-O FILM

Surface tension is known to induce smectic O (S(O)) films at the free surface of isotropic droplets of 1-methylheptyl terephthalylidene-bis- 4-aminocinnamate (MHTAC). The S(O) film has its molecules disposed in a herringbone fashion, with the layers parallel to the free surface. I t constitutes a model of a 2D polar nematic liquid crystal without any contact to solid substrates. The film is oriented uniformly when appl ying a uniform electric field, except along disclination walls. By mea suring the width of the disclination walls in the two configurations w ith the electric field parallel and perpendicular, we determine the an isotropy of the elastic constants in the induced S(O) films. We find t he ratio of the 2D bend to splay elastic constants K(b)/K(s) to be con gruent-to 0.25 which is anomalously small when compared to the corresp onding 3D ratio (K2+K3)/2K1 usually found for the bulk nematic phase. This experimental result is comparable to measurements performed with 2D suspended S(C) films with, however, a different physics.